A microturbine engine (or “microturbine”) is a type of combustion turbine engine that produces both heat and power on a relatively small scale. The component common to all microturbines is a small gas turbine engine, typically producing less than 500 kilowatts (kW) of power. This type of gas turbine comprises a single or multi-stage compressor, a combustor for liquid and/or gaseous fuels, a single or multi-stage turbine, and a power output shaft supported by a bearing system. Typically, the gas turbine is integrated with an electric generator and/or heat recovery system. Systems also generally include a housing and power and control electronics.
Microturbines designed for use with liquid fuels typically employ a prevaporizing combustor which allows liquid fuel to be vaporized in a small amount of air prior to entering the combustion zone of the microturbine combustor. However, current microturbines typically use hot combustion products to directly heat the fuel stream before it is injected into the combustor. Such systems do not permit adequate control of the heat transfer into the fuel, allowing its temperature to vary considerably during operation. This often causes fuel coking and increased combustor maintenance requirements.
Microturbines exist in a variety of sizes and can be significantly smaller and lighter than competing systems powered by reciprocating engines. However, current small, i.e., less than 25 kW, microturbines are generally inefficient and have very short lifetimes, typically less than 100 hours.